The invention concerns an interconnection of the type specified in the introductory clause of Claim 1. Coilable strips are continuously processed in sheet rolling mills or in annealing furnaces. They are located in the feed area of the mill in the form of a coil, pass through the mill, and, after they have been processed, they are rewound into a coil at the end of the mill. After the coil on the feed side has been used up, the end of the coil must be interconnected with the lead end of a fresh coil, which is then pulled through the various processing stations in the mill by the end of the first coil, as the latter continues to pass through the mill. At the end of the mill, the two strips can then be detached from one another. The finished strip can then be removed in coiled form, and, when the operation is resumed, the strip being pulled through the mill can be rewound into a coil at the end of the mill.
In the previously known equipment (U.S. Pat. No. 4,391,037), the two overlapping end sections are interconnected by means of a punching tool. The upper blade and lower blade of the punching tool make cross-shaped cuts in the two strips, and then the flaps located between two cross-shaped cuts are flanged in two layers. Due to the flanges, four layers are then positioned one above the other at the interconnection. This large thickness at the interconnections causes problems when the interconnected end sections are passed between the rolls of the mills that are processing the strip material. The interconnected punch sites have a rectangular shape, at whose rectangular corners a troublesome notch effect occurs under stress, which reduces the strength of the interconnection. The punching tools wear out after a certain amount of use and must be replaced, which is bothersome.
In addition, the production of the interconnection is time-consuming, because two stroke movements of the tool are necessary at each interconnecting site, specifically, the cutting of the two strips in a first operational phase and then flattening and pressing during the flanging of the edges of the holes in a second operational phase. Similar problems are encountered with all interconnections operating with similar stitching machines (SU 1,590,168 A1), where cross-shaped openings are formed in the overlapping end sections of the strips.
In the case of processing machines for narrow strip products made of metallic materials, it is well known that successive strips can be butt-welded. This makes it possible to obtain a flat product in the region of the interconnection, which can be passed through the processing machine without any problems. However, the welding of the interconnection changes the material properties of the product at the interconnection site. The interconnection site may be subjected to only moderate stresses.
The goal of the invention is to develop an inexpensive interconnection of the type specified in the introductory clause of Claim 1, which can be quickly produced, has a low overall height and is very strong. In accordance with the invention, this goal is achieved by the measures specified in the characterizing clause of Claim 1, which have the special significance described below.
The invention recognized that the annular welds in accordance with the invention are subject to loads on all sides. Accordingly, these welds are distinguished by high strength of the resulting interconnection under tensile loads and compressive loads. In diametric layers on all sides, i.e., including the longitudinal direction of the strip, two welds are present in an annular weld of this type, which reliably hold the position of the two layers of strips in the overlapping region flat against each other. The passage of this interconnection through processing mills with so-called S-rolls avoids the risk of the free edges turning up, even though the annular welds are located at a distance from the face ends of the two strips. The annular welds in accordance with the invention can be produced quickly and economically. The annular welds immediately withstand high tensile and compressive loads.
The annular welds may have any desired contour profile, e.g., longitudinally oval or triangular. There is no danger that the annular welds will cause notch effects, even if an angular contour profile is used. Longitudinal loads and transverse loads are immediately transmitted by the annular welds from one strip to the other without damage. A circular profile has been found to be an especially effective contour profile of the annular welds. In addition, it is recommended that the welds be formed with a hole inside the ring. The strip material at the edge around the hole then flows together to produce an especially strong interconnection between the two strips.